Field of the Invention
The present invention relates to an electro-photographic or electrostatic recording image forming apparatus utilizing a cartridge type photosensitive member.
Description of the Related Art
Hitherto, an electro-photographic image forming apparatus is configured to visualize an image by developing an electrostatic latent image formed on an image bearing member such as a photosensitive drum by resin containing coloring matters and others. Popular one among such image forming apparatuses is an image forming apparatus configured to unitize a photosensitive drum, i.e., a photosensitive member, as a cartridge, to enable the cartridge to be mounted to an apparatus body as a process cartridge or as a drum cartridge and to enable a user of the apparatus to replace the cartridge as an image forming member. It is noted that the process cartridge or the drum cartridge in which the photosensitive drum is unitized as the cartridge will be called collectively as a drum cartridge.
In order to improve workability in replacing such drum cartridge, Japanese Patent Application Laid-open No. 2016-130816 proposes an image forming apparatus configured to be able to mount the following drum cartridge. In this image forming apparatus, a cover member for protecting the photosensitive drum is attached to the new drum cartridge to be mounted to the image forming apparatus. In mounting the drum cartridge to the apparatus body, a user inserts a front end portion of the cover member into the apparatus body to be held by the apparatus body. The cover member and the apparatus body are provided respectively with guide portions configured to slidably guide the drum cartridge. The guide portion on the cover member side and the guide portion on the apparatus body side are aligned by engaging the cover member with the apparatus body. In this condition, the drum cartridge is passed from the guide portion on the cover member side to the guide portion on the apparatus body side by pressing the drum cartridge heled by the cover member into the apparatus body side by the user. In a case where the drum cartridge is inserted into the apparatus body by a first distance from an insertion starting position of the apparatus body, the apparatus body and the cover member are locked, and only the drum cartridge is inserted into the apparatus body while locking the cover member with the apparatus body.
After that, in a case where the drum cartridge is inserted into the apparatus body further and arrives at a second distance, the cover member is unlocked from the apparatus body. This arrangement makes it possible to suppress the photosensitive drum from being unnecessarily exposed and to suppress the photosensitive drum from coming into contact with the apparatus body during the drum cartridge replacing works because the drum cartridge is covered by the cover member during the drum cartridge replacing works. Still further, because the cover member is removed after mounting the drum cartridge to the apparatus body, the workability in replacing the drum cartridge is improved.
By the way, in a case where there are two types of apparatus bodies having different specifications for example, two kinds of drum cartridges having different functions of storing photosensitive drums functionally compatible with the respective apparatus bodies are prepared. At this time, there is a case where cover members of the two types of drum cartridges having the different functions are commonly used. Here, if it becomes possible for the user to replace the drum cartridge by adopting a drum cartridge replaceable with respect to the apparatus body, there is a possibility that the user erroneously inserts a drum cartridge whose cover member is identical in shape even though it is not compatible functionally with the apparatus body. Even if the user erroneously inserts such drum cartridge, there is a possibility that the user executes an image forming operation without noticing on that the drum cartridge is wrong if the shapes of the cover members and couplings are identical. In order to prevent such erroneous insertion of the drum cartridge into the apparatus body, Japanese Patent Application Laid-open No. 2004-125954 proposes an image forming apparatus provided with an erroneous insertion blocking portion that permits only a drum cartridge functionally compatible with the apparatus body to be inserted into the apparatus body. In order to prevent such erroneous insertion, this image forming apparatus is provided with uneven shaped portions for example in the apparatus body and the drum cartridge such that the uneven shaped portions interfere with each other if a wrong drum cartridge is to be inserted into the apparatus body.
However, because the drum cartridge can be inserted into the apparatus body in the image forming apparatus disclosed in Japanese Patent Application Laid-open No. 2016-130816 described above, there is a possibility that the user erroneously inserts the drum cartridge functionally incompatible with the apparatus body into the apparatus body as it is. In order to prevent such an erroneous operation, if the erroneous insertion blocking portion described in Japanese Patent Application Laid-open No. 2004-125954 is simply applied to the image forming apparatus described in Japanese Patent Application Laid-open No. 2016-130816, the following problems may occur. For instance, if the erroneous insertion blocking portion becomes operative in a case where the drum cartridge is located between the first distance where the cover member is locked by the apparatus body and the second distance where the cover member is unlocked from the apparatus body, the drum cartridge cannot be inserted into the second distance. Thereby, the cover member cannot be unlocked from the apparatus body, and depending on a configuration of the apparatus body, there is a possibility that the drum cartridge cannot be taken out of the apparatus body.
The present disclosure aims at providing an image forming apparatus which is configured to lock a cover member to an apparatus body in inserting a drum cartridge into the apparatus body and which is configured to prevent the cover member from being locked in a case where a drum cartridge functionally incompatible with the apparatus body is disabled to be inserted by an erroneous insertion blocking portion.